The invention relates to a method for improving the initial activity of hydrazine with respect to oxygen dissolved in water, in which the hydrazine is activated by adding complexes of trivalent cobalt with inorganic ligands as complex constituents.
Activated hydrazine is used as an agent to remove oxygen from water, especially from reservoir drinking water and from water which is used to preserve installations no longer in use, in order to protect containers, pipes, steam boilers, heat exchangers and other installation parts from corrosion.
Various methods are used for the removal of oxygen dissolved in water. Hydrazine has been preferred, which, when adding suitable activators, immediately reacts at low temperatures with the oxygen dissolved in water, forming innocuous nitrogen. Cationic and anionic complexes of trivalent cobalt with inorganic ligands as complex constituents are suggested as particularly suitable activators (WPC 23F/224246). Even if these activators are considered favorably, there is still the disadvantage of the concomitantly activated hydrazine not reaching its full reaction velocity with respect to the oxygen dissolved in water, immediately from the start. It has now been suggested to eliminate this deficiency either by gassing with air (WPC 23F/224247) or by adding trivalent phenols as coactivators (WPC 23F/227201). These measures result in an improvement of the initial activity, however, only when maintaining a relatively high activator concentration of 0.5 to 1 g per liter of commercial hydrazine solution. In spite of its basically good effectiveness regarding oxygen reduction, this activator concentration may still be too high for certain fields of application.
It is the object of the present invention to improve the initial activity of activated hydrazine with respect to oxygen dissolved in water, and to lower activator concentration, by using as activators, complexes of trivalent cobalt with inorganic ligands as complex constituents.